Suprapontine ablation in normal and Doc-salt or one-kidney, one-clip hypertensive rats

The role of suprapontine areas in the acute maintenance of the hypertension in awake Doc-salt (4 weeks of treatment) or one-kidney, one clip (1K-1C) (4 weeks after clipping) rats was studied. Mean blood pressure (BP) and heart rate (HR) were measured before (15 min) and after (2 hours) removing all brain tissues rostral to the pons. After this procedure no change in BP was found in normal or 1K-1C rats. In Doc-salt rats the BP falls (154 +/- 4 to 110 +/- 5 mmHg; p less than 0.001). HR was increased in normal (351 +/- 10 to 446 +/- 20 beats/min; p less than 0.01) and in 1K-1C rats (350 +/- 10 to 485 +/- 12 beats/min; p less than 0.001). Clonidine injected into the cisterna magna in 1K-1C rats after suprapontine ablation lowered BP (146 +/- 6 to 118 +/- 11 mmHg; p less than 0.05) and HR (515 +/- 17 to 400 +/- 33; p less than 0.05). Pentolinium reduced BP after the suprapontine ablation in normal (116 +/- 4 to 63 +/- 5 mmHg; p less than 0.001), Doc-salt (111 +/- 5 to 53 +/- 3; p less than 0.001) and 1K-1C rats (163 +/- 8 to 59 +/- 6 mmHg; p less than 0.001). These data suggest that suprapontine structures have an important role in the acute maintenance of Doc-salt hypertension. In 1K-1C rats the acute maintenance of hypertension depends on a sympathetic activity originated below the lesion.